The present invention relates to a device for treating preforms to obtain containers made of plastics, for example for bottles for food applications.
Currently it is known to use production apparatuses constituted by one or more separate treatment stations.
In order to optimize the production process, it is necessary to provide an apparatus for the orderly and sequential movement of the preforms, which are produced beforehand and are made for example of thermoplastic resin.
Such movement system must guide the preforms, taken in succession individually or in batches, from a loading station, along at least one heating station and optionally a blow-molding station, to the unloading station.
Depending on the type of production apparatus, the preforms must move in a vertical arrangement, with their opening directed downwardly and therefore upside down, or must move assuming different positions.
In particular, depending on the type of production apparatus, it is necessary to have a suitable movement system, which must be provided with a succession of pallets, commonly known as pick-up plugs, for the temporary interconnection of the preforms.
Prior art document WO 99/62693 is currently known. It discloses an apparatus for continuously transferring orderly sequences of preforms adapted to be converted into finished containers, comprising:
at least one closed-loop conveyor belt that constitutes guiding means for a closed-loop moving conveyor chain, which is adapted to be driven into a continuous motion
and comprises a plurality of support and forward carrying elements suitable for carrying a respective preform,
a station for loading said preforms,
an unloading station, adapted to separate the preforms from said elements,
at least one temperature conditioning station for the preforms arranged on said elements, interposed between said loading and said unloading station,
means for moving said support and forward-carrying elements along said closed-loop belt,
said support and forward carrying elements being provided with respective pick-up plugs to pick up, accommodate and release the respective preforms, characterized in that
said loading and unloading stations are arranged so that the preforms are loaded onto the pick-up plugs, and released therefrom, in a vertical position with their neck portion turned upwardly,
said support and forward carrying elements are rotated as they move between said loading station and said unloading station so that, when they move through said temperature conditioning station, the respective preforms are positioned vertically with their neck portion turned downwardly.
Moreover, FR-2,646,632 discloses devices suitable to reverse twice the orientation of the preforms, so that their neck is again directed downwardly when they are temperature-conditioned and their neck is directed upwardly for the loading and unloading steps.
The main drawback of this described known art is that these machines, usually known as xe2x80x9ccontinuousxe2x80x9d or xe2x80x9crotaryxe2x80x9d, are structurally complicated, since it is necessary, particularly for the blow-molding station, to provide components, such as the blow-molding and cooling systems, which are usually made to perform a rotation that requires a complicated cooperation with fixed radial elements such as the molds.
Moreover, these known types of machine have high production and maintenance costs and are at the same time complicated from a structural standpoint.
Machines are also known which are termed xe2x80x9cdiscontinuousxe2x80x9d and comprise two separate heating and blow-molding units; one of their drawbacks is that discontinuous heating is of the non-uniform type, and a xe2x80x9cviewxe2x80x9d effect is in fact noted in the heating of the preforms, which are placed in a fixed position in front of the heating lamps and are heated differently depending on whether they are at the center of the lamp or at its edges; furthermore, such lamps have a non-uniform emission curve along their length (emission is higher at the center).
This produces preforms that have mutually different thermal xe2x80x9chistoriesxe2x80x9d.
Italian patent no. 1,274,324 is also known which illustrates a modular apparatus that uses a moving comb that picks up the preforms, whose neck is directed upwardly, after heating them and places them at a mold for blow-molding.
The main drawback of this known apparatus is that during the heating of the preforms their neck is directed upwardly, and this is a technical problem, since the neck is a part of the preform that should remain as cold as possible.
The aim of the present invention is to solve the above noted technical problems, eliminating the drawbacks of the cited known art, by providing a device that allows to use a discontinuous machine, achieving high productivity, and to provide optimum heating, maintaining a low temperature for the neck region of the preforms, and a blow-molding that can be achieved by way of simple structural solutions and low production and management costs.
Within this aim, an object of the invention is to provide a device that allows to manage the preforms in the heating station so that their neck is directed downwardly.
Another object is to provide a device that is structurally simple and has low manufacturing costs and times.
This aim and these and other objects that will become better apparent hereinafter are achieved by a device for treating preforms to obtain containers made of plastics, characterized in that it comprises:
an ejector suitable to pick up and release one or more of said preforms, arranged so that the neck of said preforms is directed upwardly, from a heating conveyor and:
a unit for transferring said one or more preforms unloaded from said heating conveyor, which is suitable to modify spacing and speed of said preforms, adapting them to spacing and speed of an adjacent and axially offset blow-molding conveyor to which said one or more preforms are transferred.